Then we found out this is actually Broly.

YEP :)

I definitely agree, it'd be HYPE to watch Yamoshi fight off hordes of Saiyans (possible as Oozarus) for a climax. It is definitely worth noting that who ever this is, looks like fodder to Goku.
Opponent: AAAAGH I'M POWERING UP TO THE MAX!!!
Goku: Just going to casually warm-up without powering up~

True, but the movie with yamoshi everyone wants to see

There is nothing confirming that this is Yamoshi... however this does bring my attention to the fact that his arm bulks up in this scene, which makes Goku's responses funnier to me!